As a writer, director, and producer, Reynolds was involved with two highly successful CBS series in the 1970s and early 1980s. Between 1972 and 1983, he produced 120 episodes of M*A*S*H, which he co-created with Larry Gelbart, and for which he also wrote 11 episodes and directed 24. During that same period, he produced 22 episodes of Lou Grant, for which he wrote (or co-wrote) five episodes and directed 11.

Reynolds was married to actress-turned author Bonnie Jones, who appeared in five episodes of M*A*S*H as Lt. Barbara Bannerman, from 1967 until 1976, when the couple divorced. He and his current wife, actress Ann Sweeny, who also appeared on M*A*S*H as Nurse Carrie Donovan in two episodes, married in 1979 and have one son, Andrew "Buzzy" Reynolds, a semi-professional figure skater.